Aircraft brakes typically are made with a stack of alternatively interleaved stator and rotor discs, the discs being adapted for selective factional engagement with one another. The stator discs are typically splined to the axle of the aircraft, while the rotors are keyed to the wheel, generally by a series of beam keys that are circumferentially spaced about an inner portion of the wheel and that engage key slots in the outer circumferential surface of the rotors. The beam keys typically have one end thereof pinned to the wheel and an opposite end thereof mounted to an outrigger flange of the wheel.
Application Ser. No. 11/073,309, filed 7 Mar. 2005, entitled COMPOSITE WHEEL BEAM KEY, discloses wheel beam keys that are made from a mostly unidirectional carbon-carbon composite material. In addition to carbon-carbon composite materials, however, that invention also contemplates composite beam keys made with hybrid fibers (carbon or ceramic) and/or hybrid matrices (carbon or ceramic). For example, a wheel beam key of that invention may be made using two cycles of carbon densification followed by one cycle of treatment with SiC carbide or another ceramic. While the carbon-carbon composite beam keys of that invention will generally have anti-oxidant and/or wear coatings applied to them, when ceramic matrices are used, the ceramic will often provide sufficient oxidative and wear resistance.
Still another embodiment of the invention of application Ser. No. 11/073,309 is a method of manufacturing a composite wheel beam key. This method includes the steps of: forming—entirely from carbon fibers or from carbon fibers and ceramic materials—a fibrous preform blank in a shape of a desired wheel beam key: and densifying the fibrous preform to produce a carbon-carbon composite in the shape of said wheel beam key. When the fibrous preform is manufactured entirely from carbon fiber precursors, it is preferable that a majority of the fibers in the preform be oriented in the length direction of the key and a minor portion of the fibers in the preform extend in the other two perpendicular directions of the key. The resulting C—C composite wheel beam key may be immersed in antioxidant to provide an antioxidant-coaled carbon-carbon composite wheel beam key. Also, a hard, wear-resistant coating may be applied to the antioxidant-coated beam key.
In a typical embodiment of the invention described in application Ser. No. 11/073,309, the beam key is made from PAN-based carbon fibers with a carbon matrix, with the carbon matrix being densified either entirely by CVI/CVD processing or by a combination of CVI/CVD processing and pitch infiltration, followed by carbonization. Alternatively or in addition to PAN-based carbon fibers, pitch-based carbon fibers and rayon-based carbon fibers may also be used in that invention. Also, the invention of application Ser. No. 11/073,309 contemplates utilizing mixed-source carbon fibers (e.g., PAN and pitch fibers) or ceramic fibers (e.g., PAN and/or pitch and/or rayon and/or oxidized PAN and/or SiC and Al2O3 fibers), possibly combined with hybrid matrices (e.g., charred resins/CVI/charred pitch or charred phenolic with SiC, B4C, SiN, etc.). Thus that invention includes structural carbon-carbon composites, such as carbon fiber CVD-densified composites and carbon fiber CVD/pitch-densified composites and carbon fiber/phenolic-densified composites. That invention also contemplates structural carbon/ceramic composites, such as carbon/ceramic fiber combinations densified with carbon/ceramic matrices, etc. Such materials provide improved wear resistance and “built in” antioxidant properties. Examples of this approach include carbon fiber/ceramic fiber composites densified with CVD and/or pitch and/or resin, and carbon fiber and/or ceramic fiber composites densified with CVD and/or pitch and/or resin, with silicon infusion to provide SiC ceramic matrix material.
The entire disclosure of application Ser. No. 11/073,309 is incorporated by reference herein.
U.S. patent application Ser. No. 11/073,907, filed Mar. 7, 2005, entitled MOLD FIXTURE TO DENSIFY COMPOSITE BEAM KEY USING RESIN TRANSFER MOLDING, describes one way in which composite wheel beam keys such as those described in application Ser. No. 11/073,309 can be manufactured. The RTM processes in that application may involve vacuum pitch impregnation. The entire disclosure of application Ser. No. 11/073,907 is incorporated by reference herein.